lisp/textmodes/po.el

   1 ;;; po.el --- basic support of PO translation files -*- coding: utf-8; -*-
   2
   3 ;; Copyright (C) 1995-1998, 2000-2014 Free Software Foundation, Inc.
   4
   5 ;; Authors: François Pinard <pinard@iro.umontreal.ca>,
   6 ;;          Greg McGary <gkm@magilla.cichlid.com>,
   7 ;;          Bruno Haible <bruno@clisp.org>.
   8 ;; Keywords: i18n, files
   9
  10 ;; This file is part of GNU Emacs.
  11
  12 ;; GNU Emacs is free software: you can redistribute it and/or modify
  13 ;; it under the terms of the GNU General Public License as published by
  14 ;; the Free Software Foundation, either version 3 of the License, or
  15 ;; (at your option) any later version.
  16
  17 ;; GNU Emacs is distributed in the hope that it will be useful,
  18 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  19 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20 ;; GNU General Public License for more details.
  21
  22 ;; You should have received a copy of the GNU General Public License
  23 ;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.
  24
  25 ;;; Commentary:
  26
  27 ;; This package makes sure visiting PO files decodes them correctly,
  28 ;; according to the Charset= header in the PO file.  For more support
  29 ;; for editing PO files, see po-mode.el.
  30
  31 ;;; Code:
  32
  33 (defconst po-content-type-charset-alist
  34   '(("ASCII" . undecided)
  35     ("ANSI_X3.4-1968" . undecided)
  36     ("US-ASCII" . undecided))
  37   "Alist of coding system versus GNU libc/libiconv canonical charset name.
  38 Contains canonical charset names that don't correspond to coding systems.")
  39
  40 (defun po-find-charset (filename)
  41   "Return PO charset value for FILENAME.
  42 If FILENAME is a cons cell, its CDR is a buffer that already contains
  43 the PO file (but not yet decoded)."
  44   (let ((charset-regexp
  45          "^\"Content-Type:[ \t]*text/plain;[ \t]*charset=\\(.*\\)\\\\n\"")
  46         (buf (and (consp filename) (cdr filename)))
  47         (short-read nil))
  48     (when buf
  49       (set-buffer buf)
  50       (goto-char (point-min)))
  51     ;; Try the first 4096 bytes.  In case we cannot find the charset value
  52     ;; within the first 4096 bytes (the PO file might start with a long
  53     ;; comment) try the next 4096 bytes repeatedly until we'll know for sure
  54     ;; we've checked the empty header entry entirely.
  55     (while (not (or short-read (re-search-forward "^msgid" nil t) buf))
  56       (save-excursion
  57         (goto-char (point-max))
  58         (let ((pair (insert-file-contents-literally filename nil
  59                                                     (1- (point))
  60                                                     (1- (+ (point) 4096)))))
  61           (setq short-read (< (nth 1 pair) 4096)))))
  62     (cond ((re-search-forward charset-regexp nil t) (match-string 1))
  63           ((or short-read buf) nil)
  64           ;; We've found the first msgid; maybe, only a part of the msgstr
  65           ;; value was loaded.  Load the next 1024 bytes; if charset still
  66           ;; isn't available, give up.
  67           (t (save-excursion
  68                (goto-char (point-max))
  69                (insert-file-contents-literally filename nil
  70                                                (1- (point))
  71                                                (1- (+ (point) 1024))))
  72              (if (re-search-forward charset-regexp nil t)
  73                  (match-string 1))))))
  74
  75 (defun po-find-file-coding-system-guts (operation filename)
  76   "Return a (DECODING . ENCODING) pair for OPERATION on PO file FILENAME.
  77 Do so according to FILENAME's declared charset.
  78 FILENAME may be a cons (NAME . BUFFER).  In that case, detect charset
  79 in BUFFER."
  80   (and
  81    (eq operation 'insert-file-contents)
  82    (or (if (consp filename) (buffer-live-p (cdr filename)))
  83        (file-exists-p filename))
  84    (with-temp-buffer
  85      (let* ((coding-system-for-read 'no-conversion)
  86             (charset (or (po-find-charset filename) "ascii"))
  87             assoc)
  88        (list (cond
  89               ((setq assoc
  90                      (assoc-string charset
  91                                    po-content-type-charset-alist
  92                                    t))
  93                (cdr assoc))
  94               ((or (setq assoc (assoc-string charset coding-system-alist t))
  95                    (setq assoc
  96                          (assoc-string (subst-char-in-string ?_ ?-
  97                                                              charset)
  98                                        coding-system-alist t)))
  99                (intern (car assoc)))
 100               ;; In principle we should also check the `mime-charset'
 101               ;; property of everything in the base coding system
 102               ;; list, but there should always be a coding system
 103               ;; corresponding to the MIME name.
 104               ((featurep 'code-pages)
 105                ;; Give up.
 106                'raw-text)
 107               (t
 108                ;; Try again with code-pages loaded.  Maybe it's best
 109                ;; to require it initially?
 110                (require 'code-pages nil t)
 111                (if (or
 112                     (setq assoc (assoc-string charset coding-system-alist t))
 113                     (setq assoc (assoc-string (subst-char-in-string
 114                                                ?_ ?- charset)
 115                                               coding-system-alist t)))
 116                    (intern (car assoc))
 117                  'raw-text))))))))
 118
 119 ;;;###autoload
 120 (defun po-find-file-coding-system (arg-list)
 121   "Return a (DECODING . ENCODING) pair, according to PO file's charset.
 122 Called through `file-coding-system-alist', before the file is visited for real."
 123   (po-find-file-coding-system-guts (car arg-list) (car (cdr arg-list))))
 124 ;; This is for XEmacs.
 125 ;(defun po-find-file-coding-system (operation filename)
 126 ;  "\
 127 ;Return a Mule (DECODING . ENCODING) pair, according to PO file charset.
 128 ;Called through file-coding-system-alist, before the file is visited for real."
 129 ;  (po-find-file-coding-system-guts operation filename))
 130
 131 (provide 'po)
 132
 133 ;;; po.el ends here